I'm pretty sure that your problem is the name of the fields, and not the syntax. Try something like this

Try
   Alter table...
Catch
   Wait 'Oldname with error is '+m.oldname window
   Wait 'Newname with error is '+m.newname window
Endtry

Then you write down the wrong values, and tell me what they are.

>sorry i don't now what you main, or how i can know(to get) the value for OldName and NewName
>What is the value of OldName when you get this error?
>What is the value of NewName when you get this error?
>
>>Please answer my two simple questions!
>>
>>>if you main when i make replace via textboxes it's characters and numbers ,
>>>
>>>if you main excel sheet i have some fields have numbers ,and some fields have characters and ONE field have first record as blabla and next as #
>>>
>>>
>>>
>>>>What is the value of OldName when you get this error?
>>>>What is the value of NewName when you get this error?
>>>>